Synopsis: Trans-generational Epigenetic Inheritance means your environment may affect your genetics in ways that can be passed down to your children.

Trans-generational Epigenetic Inheritance

The idea that epigenetic marks (DNA methylation, histone modifications) can be acquired on the DNA of one generation and stably passed on through the gametes (sperm and eggs) to the next generation. In other words, experiences and environmental exposures can change the way your DNA works (without changing the DNA itself) and this could be passed on to your offspring.

Epigenetic Inheritance - The transmittance of information from one generation to the next that affects the traits of offspring without alteration of the primary structure of DNA (the sequence of nucleotides) or from environmental cues.

Epigenetic inheritance - Used to describe both cell-cell and organism-organism information transfer, while trans-generational epigenetics typically refers only to the latter. Although these two levels of epigenetic inheritance are equivalent in unicellular organisms, they may have distinct mechanisms and evolutionary distinctions in multicellular organisms.

Main Document

"Fear actually may be a partly inherited trait, one programmed into our genetic makeup, according to a study of twins."

Science has discovered that the fears a parent experiences can be passed down to their children. The results of experiments with mice suggest that fallout from a person's traumatic experiences may extend through generations. The study was a particularly interesting one.

Mouse parents learned to associate the smell of orange blossoms with an electric shock.

The children of these mice and their grandchildren startled in response to the scent, a sign of fear, even though they had never smelled the scent before in their lives. Mice children also had more neurons that detect the orange blossom smell than mice whose parents were not exposed to the smell.

Sperm cells alone have the ability to deliver the message of fear, according to Kerry Ressler and Brian Dias at Emory University. The DNA in sperm cells was imprinted with the association of fear. A gene that codes for the molecule that detects the smell of orange blossoms carried a chemical stamp that might have changed its behavior.

Information stemming from parent's experiences might be important in relation to survival.

Being aware that a certain smell signals a rough shock could help an animal avoid trouble without having to experience the shock firsthand. The experiences of our ancestors may be an under-appreciated influence on the brains of both animals and people, as well as our behaviors, according to Kerry and Brian. The discovery shows the multi-generational effects of:

About This Image: Regions of the brain affected by PTSD and stress.From a scientific perspective this is referred to as, 'Trans-generational Epigenetic Inheritance.' What this means; in essence, is that your environment may affect your genetics in ways that can be passed down to your children. The finding might lead to a completely new understanding of some forms of mental illnesses and could at least partially explain the increasing rates of some disorders.

A Study of Twins and Fear

Fear is something long thought to be a learned response.

Fear actually may be a partly inherited trait, one programmed into our genetic makeup, according to a study of twins. Dr. John Hettema of Virginia Commonwealth University in Richmond, Virginia along with colleagues from Sweden, studied 90 pairs of identical twins and 83 pairs of fraternal, or non-identical twins, enrolled in the Swedish Twin Registry. Identical twins have exactly the same genes, yet fraternal twins are genetically different; as different as children born separately from the same parents.

In the study, the twins were shown a series of different images. Some of the images were naturally frightening - such as spiders and snakes. Other images were neutral such as triangles and circles. The twins were also given a mild electrical shock as they viewed some of the images.

During the testing, researchers measured the subject's skin electrical conductivity, which usually increases in states of fear and anxiety due to increased output from the person's sweat glands. When the researchers analyzed the results, they found that the identical twins had the same responses. They also discovered the non-identical twins experienced differing responses.

Traditionally, fear is something that has been thought of as a learned response. A person endures a frightening experience and then learns to be anxious and apprehensive when it happens, or the potential for it to happen again arises. The process is referred to as, 'conditioning.'

Dr. Hettema said, "Now can say that the fear conditioning process in humans is controlled, at least to some extent, by genetic factors. Between one-third and one-half of the fear conditioning process appears to be inherited." Fear is a desirable and natural response to dangerous situations. Yet when a person's fear is out of proportion to the stimulus that caused it, or is debilitating or chronic, a person may be said to be suffering from an anxiety disorder. Understanding the genetic basis of fear could assist future researchers with development of treatments for conditions such as anxiety and phobia states, according to Dr. Hettema.

Thoughts Concerning These Results

It is amazing to find scientists suggesting that people can inherit fears, but it seems the results are what they are. The results of these experiments suggest many things. For example; it is perhaps not so unusual that both a father and son are afraid of spiders, or that a mother and daughter are frightened by snakes - even though they have no real reason to be.

The studies also suggest something far more large scale. For example; children of those who fought in wars may experience the same or similar trauma their parents do. If the studies are proven correct in the long-term, even the grandchildren of those who have endured a war may experience PTSD similar to the PTSD their grandparents do or did.

Is there a, 'compounding,' factor at play? One has to wonder. If the people of a certain nation are repeatedly exposed to shelling, bombing, and other violent military activity - do repeated exposures to such violence, 'compound,' thereby worsening the fears and trauma their children and grandchildren experience? Perhaps one day science will tell us.

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